Walther A115 Prototype Rifle

The Walther A115 was one of the semiauto rifles developed in pre-WWII Germany. Apparently only three were made, and it uses a neat combination of sheet metal construction with a rotating bolt and annular gas pistol like the later G41 rifles. This particular example was examined by Aberdeen Proving Ground in 1955 (you can find their photos of it around) before escaping into the private market.